The studies described in his thesis are certainly the first to explore concurrently the evolutionary, environmental and biotic forces that shape beetle community assembly and distribution, and are among the few that have assessed how beetles recolonise secondary forest habitat across the world. In a world where habitats are becoming increasingly fragmented these types of studies are going to become even more important. My thesis has barely scratched the surface in terms of understanding the complex forces operating on beetles. There are of course large knowledge gaps, but some general areas that seem particularly worthy for future research relate to beetle taxonomy and habitat requirements, forest management, future development of the beetle functional trait paradigm and expanding our understanding of community assembly. Filling these knowledge gaps will not only allow for more effective
management of this diverse group of organisms, but also may help generate assembly rules that can help further understand and predict how communities responds to disturbance.
6.2.1 The taxonomic impediment and habitat requirements
Some of the biggest challenges faced by invertebrate conservation biologists across the world, but particularly outside of Europe, include the difficulty in species
identification and the lack of species-level knowledge about habitat requirements and distribution. For example, even in this relatively well studied system (for Australian standards) the majority of species lack formal description and very little is known
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about their habitat requirements and distribution. Using molecular data to delimit and identify species has the potential to help overcome the taxonomic impediment
(Monaghan et al., 2005; Pons et al., 2006). Coupled with thorough DNA inventory using metagenomic approaches (e.g. Zhou et al., 2013) to identify both beetle species and other invertebrates in wet forests, our knowledge of beetle distribution and diversity would greatly increase. Considering the large number of beetle species even in this temperate system, gaining insights into species habitat requirements and life history may be a more difficult proposition. As I mentioned in Chapter 1, molecular and metabolomic approaches may offer a shortcut to gain insights into the habitat requirements and life history aspects of a species. For example, quantitative trait approaches can identify particular genes associated with insect fecundity (Leips et al., 2006). However, in the short term at least, increased autecological work is
required. Such knowledge can help determine which species may decline in response to forest management (Didham et al., 1998; Henle et al., 2004; Baker et al., 2007). 6.2.2 Forest management
As forest influence is still a relatively new concept there are wide gaps in our understanding. The optimal size of retained mature forest remnants, for example, is likely to be important for beetle recolonisation in the long term but is currently unknown. Within beetle metapopulations, for example, local patch size has been shown to determine beetle colonisation into burnt habitat, with larger patch sizes leading to higher colonisation of burnt forest (Ranius et al., 2014). If small mature forest aggregates reduce recolonisation success, forest influence may not extend as far as I have suggested. Understanding how mature forest patch size impacts forest influence will be important for designing effective aggregated retention systems. As beetles communities exhibit strong fluctuations in species compostion throughout the year, understanding how forest influence may change temporally is also
apotentially significant. For example, the microclimate gradient across forest edges is most extreme during the summer months, even ~45 years after logging (Baker, in press), and this may follow on to differential forest influence effects on beetles. Also,
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forest edges may be less permeable in summer and species that disperse at this time maybe more restricted to mature forest habitat.
Perhaps more importantly, how forest influence impacts ecosystem processes is also an open question. Beetles are key components of the leaf litter biome and play an important role in ecosystem processes such as nutrient cycling (Nichols et al., 2009; Zhao et al., 2013). Nutrient cycling is known to change as forest succession proceeds (e.g. Vitousek, 1984), but assessing how differences in invertebrate communities can alter this process is unknown. If forest influence does have an effect on ecosystem processes, this would suggest that there is more to aggregated retention than just biodiversity conservation alone. An increased understanding of beetle ‗effect traits‘ (Díaz et al., 2013) could be one approach to answering this question.
6.2.3 Future functional trait work and community assembly
I have demonstrated how functional trait syndromes change during forest succession in Tasmanian wet forest, but understanding to what extent this pattern is more general for similar trophic groups across the world is an important next step. In deciduous forest, for example, I expect the pattern may be quite different due to the seasonal fluctuations in canopy coverand leaf litter inputs. Also understanding if ‗hard‘ traits or different trait sets lead to different results is also important step for arthropod trait studies. Nonetheless, As plant studies have demonstrated (e.g. López- Martínez et al., 2013), functional trait syndromes applicable across a variety of ecosystems are both a useful short cut to understand ecosystem recovery, but may also give insight to what evolutionary and environmental forces may be shaping species.
Finally, developing consistent trait approaches for other arthropod groups would also provide greater insights into their ecology, and would test how general these
syndromes are. For example, as most of the traits used in this thesis are applicable to other arthropod groups, it is possible that some traits may respond in a similar fashion e.g. relative leg length and eye size. Furthermore, applying a combined functional trait and phylogenetic approach to other animal taxa would also test if
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similar environmental and evolutionary forces act on all communities living amongst the undergrowth.